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Do Gluten-Free, Sugar-Free, or Low-Carb Diets Actually Work?

Date:Wednesday, June 13, 2018

Ginny Graves and Marissa Miller

When it comes to food, Americans often bounce between extremes: We go all in on the Thanksgiving stuffing, then cut out entire food groups in an attempt to "compensate." It's unsurprising that gluten-, dairy-, and sugar-free diets, which were intended for people with legitimate health concerns, have gone mainstream. Their proponents say they improve the complexion, improve alertness and mood, and "detox" the body (spoiler alert: our bodies naturally do that for us).

Many restrictive plans require intense commitment, which, in a strange twist, might be part of their draw: "Avoiding a food group altogether can seem easier than trying to eat it in moderation," says Lisa Young, an adjunct professor of nutrition at New York University and the author of The Portion Teller Plan.

But austerity isn't the only reason eliminating foods has gained traction in recent years. Many devotees are attracted by celebrity enthusiasm: Stars including Jessica Alba and Kim Kardashian have praised gluten-free eating, for example, with Kardashian once tweeting, "Gluten free is the way to be." So when is the effort to adhere to a gluten-, sugar-, or dairy-free diet worth it? And how about the paleo diet, which shuns grains, dairy, and refined sugar (not to mention legumes and processed foods)? We asked the experts — read on for their take on each of these eating approaches.

1. Gluten-free

The scoop: Gluten is a protein found in wheat, barley, and rye. Translation: It's in tons of stuff, including bread, pasta, cereal, crackers, beer, and many salad dressings, soups, and soy sauces. Gluten-free eaters learn to love alternative grains like amaranth, buckwheat, quinoa, and rice, but only those with a wheat allergy or, more seriously, ­celiac disease, must strictly comply. When people with celiac disease eat gluten, it sets off an immune reaction that damages the lining of the small intestine, causing diarrhea, gas, bloating, and other symptoms like irritability, muscle cramps, skin rashes, anemia. (A blood test and an intestinal biopsy can confirm a celiac diagnosis; Keri Gans, a registered dietitian and the author of The Small Change Diet, advises against eliminating gluten from your diet before being tested in order to avoid a false negative.)

Celiac disease affects about three million people in the U.S., but far more — as many as 20 million — are estimated to have non-celiac gluten sensitivity. That means eating foods like bread or pasta leaves them bloated, foggy, depressed, and headache-y. "Some people eat gluten safely for 20, 30, or 40 years, then suddenly develop a problem," says Alessio Fasano, director of the Center for Celiac Research and Treatment at MassGeneral Hospital for Children. Since no reliable sensitivity test is yet available, the only way to determine whether your malaise is gluten-related is to try the diet and see if you feel better, which should be apparent within a few days.

Benefits: Those with celiac or pronounced gluten sensitivity will see the most improvement. "Brain fog, bloating, and headaches should go away immediately," says Fasano. "Many people feel remarkably better." Since gluten sensitivity can trigger an inflammatory response that leads to acne, rosacea, or eczema, omitting it from your diet could help clear up your skin, as cosmetic dermatologist Fredric Brandt told Allure in 2013. But if you don't have a true gluten sensitivity, you're not likely to notice any changes in your mood, skin, or gut.

Drawbacks: You may end up eating more calories than your body needs. Thanks to the gluten-free trend, there is now a glut of G-free muffins, pies, cakes, and pizzas with relatively little nutritional merit. Some of these substitutes are more caloric than their standard counterparts because manufacturers use corn or potato starch to add texture, explains Susan Bowerman, Director of Nutrition Training at Herbalife, International.

Some experts also believe that avoiding gluten could potentially set you up for a vitamin deficiency: Wheat is rich in thiamine and other B vitamins, says Cynthia Kupper, executive director of the Gluten Intolerance Group of North America, and B vitamins "are important for the health of your hair, skin, brain, and nerves." If you're not eating wheat, it's important to get those vitamins from other places. (What's more, gluten-free foods can cost two or three times as much as conventional ones.)

Bottom line: People who can't eat gluten now have a greater variety of appealing choices than ever. Everyone else can skip the gluten-free diet and count their blessings.

2. Dairy-free

The scoop: Swearing off dairy entirely is harder than it sounds. It means avoiding not only milk, cheese, and yogurt (did we mention cheese?) but many other foods, including energy bars, sausage, and baked goods. More than 50 million Americans are lactose intolerant: They lack sufficient enzymes to help digest lactose, the sugar in dairy products, and so the lactose stays in the belly. There, bacteria devour it with unpleasant results, like diarrhea, gas, and cramping.

Still, most people don't need to go totally dairy-free, according to Andrea Giancoli, a registered dietitian. Even people who have trouble with lactose "often can tolerate a little dairy, and many can eat hard cheeses because they have less liquid whey, and, as a result, lower lactose. Yogurt is often OK, too, because the bacteria predigest some of the sugar." If you suspect you have lactose intolerance, your doctor can confirm with one of a few tests. (Gans notes that a milk allergy can be life-threatening, so it's smart to opt for testing under the supervision of a doctor.)

The recent championing of dairy-free diets is driven by more than lactose intolerance, though: Concerns about animal welfare and even a desire to save money influence people's decisions to give up dairy (skipping your daily latte seems like an easy way to cut back on spending, for example). After food journalist Mark Bittman wrote about his experience with dairy consumption and chronic heartburn for the New York Times, he shared that he received hundreds of comments from readers claiming that eating no dairy had alleviated everything from migraines to nasal congestion. "Those effects aren't rooted in science, but there is some ­anecdotal evidence," says Young.

Benefits: If you have lactose intolerance, you're naturally going to feel a whole lot better when you cut out lactose out. You'll notice a decrease in bloating and gas, heartburn, and headaches — and your skin might clear up too, Brandt told us in 2013: "Hormones in milk increase the level of androgens in your body, and that triggers the production of oils that clog pores." Moreover, the sugar in dairy products causes the body to release insulin-like growth factor, which triggers inflammation and breaks down collagen and elastin.

Drawbacks: Calcium and vitamin D are crucial for maintaining bone health as you age. It's not guaranteed that milk alternatives like almond and coconut will contain levels of these nutrients on par with their dairy counterparts, so keep reading labels and get informed about how to make up for any nutritional shortfalls elsewhere. "If you remove dairy from your diet, you need to eat plenty of leafy greens and possibly take a [vitamin] D supplement to make up for it," Bowerman says.

Bottom line: Those who can't tolerate lactose or don't want to consume animal products can easily do without dairy. If you don't have a diagnosable problem but find that you feel better without the stuff, you're safe disavowing dairy, too.

3. Sugar-free

The scoop: Eliminating sugar from your diet is a little like getting pollen out of your air supply. It's everywhere: in ketchup, barbecue sauce, granola, cereal, flavored yogurt, sports drinks, instant oatmeal, energy bars, and more. But if you limit obvious sources — for example, soda, ­candy, and baked goods — along with most processed foods, you can go a long way toward reducing the 77 pounds of the stuff each of us consumes on average per year.

Although friends who want to split the crème brûlée might object, no nutritionist will. Some scientists actually go so far as to call added sugar "poison," an idea that has gained widespread popularity among health experts and physicians in recent years. "They may not be that far off," admits Jana Klauer, a New York City physician and the author of The Park Avenue Nutritionist's Plan. "Sugar can contribute to mood swings, weight gain, and, over time, insulin resistance, and there's almost certainly an addictive quality for some people. They have one bite and it opens the floodgates; all they want is more."

Benefits: Cutting out sugar can stabilize your mood: That's because sugar causes glucose — and energy — to spike, then plummet. Eliminating the stuff can also reduce stress on your body and skin: "Glucose can trigger enzymes that break down tissues, including the collagen and elastin in your skin," says Jessica Wu, a Los Angeles dermatologist and the author of Feed Your Face.

Drawbacks: There's a caveat to the "sugar is bad" conclusion: Gans says not all sugar is created equal and points to the example of the naturally occurring sugar in whole fruits, which are a healthy source of essential nutrients including vitamin C, potassium, and folate.

Bottom line: Choosing to go sugar-free is likely to help boost your mood and increase energy, and if you can't bear to take it that far, merely cutting back can be good medicine. For those with a sweet tooth, Gans says that all foods can fit into a healthy, well-balanced diet, even sugar.

Benefits: Lisa Sasson, clinical associate professor of nutrition and food studies at New York University, says that one of the benefits of making sure you get enough protein is that you feel fuller longer: Protein generally takes longer to digest than carbohydrates or fats. The focus that paleo puts on whole fruits and vegetables, meanwhile, means you're more likely to get plenty of the vitamins, minerals, antioxidants, and fiber they contain, she adds; cutting out processed foods high in sodium, sugar, and preservatives is a good move for your health, too. (That said, as Gans has told Allure, it's worth getting specific about what it means when we say a food is "processed." For example, even "raw " almonds go through pasteurization, a form of processing, before we eat them, and they're still a much healthier snack than Fritos.)

Drawbacks: It's possible for you to miss out on key nutrients while adhering to a paleo diet, Sasson says, including calcium and vitamin D from dairy and B vitamins from grains, as described above. What's more, she points out that if you're getting your protein primarily from red meat, you run the risk of consuming too much cholesterol and saturated fat, which is a heart-healthy risk. Finally — and this is an important one — you could miss out on foods that you genuinely like and that are also safe for you to eat. Feeling deprived isn't a sustainable way to live.

Bottom line: Focusing on whole foods is always a good idea, but cutting out entire food groups paleo-style may make it more difficult for you to get the nutrients you need and the enjoyment that makes a diet last. Still, at the end of the day, everyone is different: Listening to your body and working with your health care provider will help you figure out the best ways to nourish yourself.